Muscles of mastication

muscles of mustication: 3d representation

1. NAME: Dr. SHRUTI SUDARSANAN DEPT OF PEDODONTICS AND PREVENTIVE DENTISTRY SEMINAR TOPIC: MUSCLES OF MASTICATION

2. MUSCLES OF MASTICATION

3. INTRODUCTION The muscles of mastication move the mandible during mastication and speech.

4. DEVELOPMENT They develop from the mesoderm of the first branchial arch , and are supplied by the mandibular nerve which is the nerve of that arch.

5. MASSETER MUSCLE Quadrilateral Lateral surface of Ramus of mandible has three layers Superficial layer Middle layer Deep layer

6. MASSETER MUSCLE Superficial layer : Origin: Anterior 2/3 rd of lower border of zygomatic arch and adjoining zygomatic process of maxilla Fibres : pass downwards and backwards 45 degree Insertion: Lower part of lateral surface of mandibular ramus

7. Middle layer : Origin: Lower border of posterior 1/3 rd of zygomatic arch Deep layer : Origin: Deep surface of zygomatic arch FIBRES : pass vertically downwards INSERTION : Ramus of mandible

8. Action of masseter muscle Elevates the mandible to close the mouth and to occlude the teeth in mastication. Superficial fibres cause little protraction

9. Clinical importance of masseter muscle Masseter muscle hypertrophy is a rare condition of idiopathic cause It clinically presents as an enlargement of one or both masseter muscle Most patients complain of facial asymmetry

10. TEMPORALIS MUSCLE Large fan shaped fills the temporal fossa Origin (a)temporal fossa (b)temporal fascia FIBRES: Anterior fibres: run vertically Middle fibres: obliquely Posterior fibres: horizontally Insertion (a) coronoid process (b)anterior border of ramus of mandible

11. ACTION OF TEMPORALIS MUSCLE Elevation of the mandible Posterior fibers draw the mandible backwards after it has been protruded. Helps in side to side grinding movement

12. LATERAL PTERYGOID MUSCLE Short, Conical 2 Heads :- Upper And Lower Head Origin: Upper head (small)– from infratemporal surface & crest of greater wing of sphenoid bone Lower head (larger) – from lateral surface of lateral pterygoid plate

13. MEDIAL PTERYGOID PLATE LATERAL PTERYGOID PLATE MEDIAL SURFACE LATERAL SURFACE LATERAL PTERYGOID MUSCLE MEDIAL PTERYGOID MUSCLE

14. Insertion : Upper head - pterygoid fovea on the anterior surface of neck of mandible Lower head - anterior margin of articular disc & capsule of TMJ

15. ACTIONS OF LATERAL PTERYGOID FIBRES: Run backward and laterally depresses the mandible protrudes it forward for opening of the jaw right lateral pterygoid turn the chin to left side as part of grinding moments O I O

16. Clinical importance of lateral pterygoid muscle: Most commonly involved muscle in Myofacial pain dysfunction syndrome ( mpds ) Unilateral failure of lateral pterygoid muscle to contract results in deviation of the mandible toward the affected side on opening Bilateral failure results in limited opening, loss of protrusion and loss of full lateral deviation

17. MEDIAL PTERYGOID MUSCLE Quadrilateral Has a small superficial and large deep head

18. Origin : Superficial head: it arises from the maxillary tuberosity and adjoining bone Deep head: from medial surface of lateral pterygoid plate and adjoining process of palatine bone

19. FIBERS: run backwards, downwards and laterally Insertion: Roughened area on the medial surface of angle and adjoining ramus of the mandible below and behind the mandibular foramen and mylohyoid bone

20. ACTIONS OF MEDIAL PTERYGOID elevates the mandible closes the jaw helps to protrude the mandible Right medial pterygoid with right lateral pterygoid turn the chin to left side as part of grinding moments

21. Clinical importance : commonly involved in MPDS Trismus following inferior alveolar nerve block is mostly due to involvement of medial pterygoid muscle

22. OKESON’S CLASSIFICATION OF MASTICATORY MUSCLES DISORDERS Masticatory Muscle Disorders 1. Protective Co-Contraction 2. Local Muscle Soreness 3. Myofascial Pain 4. Myospasm 5. Chronic Centrally Mediated Myalgia Trauma and excessive use of muscles

23. Protective co-contraction a CNS response to injury or threat of injury. protective muscle splinting. In the presence of an injury or threat of injury, normal sequencing of muscle activity seems to be altered to protect the threatened part from further injury. This coactivation of antagonistic muscles is thought to be a normal protective or guarding mechanism . If protective co-contraction continues for several hours or days, the muscle tissue can become compromised and a local muscle problem may develop

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25. Local muscle soreness Local muscle soreness is a primary, noninflammatory, myogenous pain disorder (i.e., noninflammatory myalgia). first response of the muscle tissue to prolonged co-contraction. Although co-contraction represents a CNS-induced muscle response, local muscle soreness represents a condition characterized by changes in the local environment of the muscle tissues. These changes are characterized by the release of certain algogenic sub-stances (i.e., bradykinin, substance P, and even histamine) that produce pain

26. Local muscle soreness presents clinically with muscles that are tender to palpation increased pain with function. Structural dysfunction is common limited mouth opening results when the elevator muscles are involved.

27. Management Eliminate any ongoing source of deep pain input (whether dental or other) Advise the patient to restrict mandibular use to within painless limits The patient should be encouraged to reduce any nonfunctional tooth contacts   The patient should be made aware of the relationship between increased levels of emotional stress and the muscle pain condition When nighttime clenching or bruxing is suspected (early-morning pain), it is appropriate to fabricate an occlusal appliance for nighttime use of a mild analgesic: aspirin, acetaminophen, or another NSAID (i.e., ibuprofen)

28. Myospasms (Tonic Contraction Myalgia) involuntary CNS-induced tonic muscle contraction often associated with local metabolic conditions within the muscle tissues. it is not as common History The patient reports a sudden onset of restricted jaw movement usually accompanied by muscle rigidity. Treatment Myospasms are best treated by reducing the pain and then passively lengthening or stretching the involved muscle attempts to eliminate the etiologic factors

29. Myofascial Pain (Trigger-Point Myalgia) Myofascial pain is a regional myogenous pain condition characterized by local areas of firm, hypersensitive bands of muscle tissue known as  trigger points Clinical characteristics ( laskin’s cardinal symptoms ) of mpds Pain or discomfort anywhere about the head or neck. Limitation of motion of the jaw. Joint noises– grating, clicking, snapping. Tenderness on palpation of the muscles of mastication

30. management Eliminate any source If a sleep disorder is suspected, proper evaluation and referral should be made. Often low dosages of a tricyclic antidepressant, such as 10 to 20 mg of amitriptyline before bedtime, can be helpful treatment and elimination of the trigger points. This is accomplished by painlessly stretching the muscle containing the trigger points. The following techniques can be used to achieve this. Spray and Stretch Pressure and Massage Ultrasound and Electrogalvanic Stimulation Injection and Stretch

31. Centrally Mediated Myalgia (Chronic Myositis) chronic, continuous muscle pain disorder originating predominantly from CNS effects that are felt peripherally in the muscle tissues. This disorder presents clinically with symptoms similar to those of an inflammatory condition of the muscle tissue; therefore it is sometimes referred to as myositis. Management: Restrict use of the mandible to within painless limits.  Avoid exercise and/or injections Disengage the teeth Begin using an anti-inflammatory medication. Consider management of sleep

32. TRISMUS Tonic contraction of the muscles of mastication- ( taber’s cyclopedic medical dictionary) Reduced mandibular range of motion due to contraction of muscles of mastication Various criteria for presence of trismus: Mouth opening <20mm ( jen et. Al., 2002) Mouth opening <40mm ( nguyen et. Al., 1988) Severity scales: mild, >30mm; moderate, 15-30mm; severe, <15mm ( thomas et. Al., 1998

33. Treatment: Removal of the cause Heat therapy Warm saline rinses Nsaids Passive muscle stretching exercises

34. Bruxism is an abnormal repetitive movement disorder characterized by jaw clenching and tooth gnashing or grinding. It is classified into two overlapping types: awake bruxism (AB) and sleep bruxism (SB). Treatment: Coronoplasty Maxillary stabilization appliance Night guards

35. Diverse methods used in physical therapy improve muscle pain and activity, mouth opening, oral health, anxiety, stress, depression, temporomandibular disorder, and head posture in individuals with bruxism

36. CONCLUSION The masticatory muscles include a vital part of the orofacial structures and are important both functionally and structurally Precise movement of mandible by the musculature is required to move the teeth accurately across each other during function The knowledge of the anatomy physiology and mechanism of these muscles are basic to understand the movements It is crucial responsibility of a clinician to recognize each patient’s muscular environment and be aware of the problems related with excessive or deficient use of muscle and their bearing to the dentition

37. Botulinum toxin (BTX) is a neurotoxin, and its injection in masticatory muscles induces muscle weakness and paralysis. This paralytic effect of BTX induces growth retardation of the maxillofacial bones, changes in dental eruption and occlusion state, and facial asymmetry

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